Genic Variability and Differentiation in the Galapagos Finches

Electrophoretic methods were used to examine patterns of genic variation within and between populations of 11 species of Galapagos finches (Geospizinae) and to examine phyletic relationships among these species. Levels of genetic heterozygosity are moderate and are similar to those found for other vertebrates, including birds. Interpopulation levels of genic differentiation are slight for all species except the Warbler Finch (Certhidea olivacea), which exhibits marked differentiation. Nevertheless, the island populations of finch species are several times more differentiated than are populations of mainland avian species. The patterns of both within and between population genic variation are most easily explained as functions of population size and the degree of interisland movements. The relationships among the finch taxa suggested by the biochemical data are quite concordant with the traditional view based on morphology.